Winston A. S. Banya

Atopy, intestinal helminth infection and total serum IgE in rural and urban adult Gambian communities

Background The rarity of atopy in traditional societies has been attributed to high parasite‐driven blocking IgE concentrations. Information is lacking on the relationship between atopy, IgE and intestinal helminth infection in African populations.

Nasopharyngeal carriage of pneumococci in Gambian children and in their families.

BACKGROUND Nasopharyngeal carriage of pneumococci is prevalent among children in developing countries but little is known about the relationship of nasopharyngeal carriage to invasive disease or about the way in which pneumococci spread within households. OBJECTIVES To determine the prevalence of nasopharyngeal carriage in healthy and sick Gambian children and to investigate transmission within households. METHODS Nasopharyngeal swabs were obtained by the per nasal route and cultured for pneumococci on selective media. Pneumococci were serotyped with the use of latex particles coated with type-specific antisera. RESULTS Pneumococci were isolated from the nasopharynx of 73 (90.1%) of 81 children with invasive pneumococcal disease, 86 (76.1%) of 113 healthy, age-matched control children and 911 (85.1%) of 1071 sick children. Pneumococci belonging to serotypes 1, 14 and 12 were isolated significantly more frequently from cases than from matched controls. In 43 (76.8%) of 56 children with invasive disease, pneumococci isolated from the nasopharynx and from the blood or other sterile site belonged to the same serotype. Pneumococci of the same serotype as the bacterium responsible for invasive disease in a child were obtained from 72 (8.5%) of 843 family members, most frequently from young siblings of the case patients. CONCLUSION Nasopharyngeal carriage of pneumococci is more prevalent among young Gambian children than among adults and invasive infections are probably acquired more frequently from siblings than from parents. However, further studies are needed to confirm this hypothesis with more discriminating markers than polysaccharide serotyping.

Family history: an opportunity for early interventions and improved control of hypertension, obesity and diabetes

OBJECTIVE To examine whether a family history of high-risk groups for major noncommunicable diseases (NCDs) was a significant risk factor for these conditions among family members in a study population in the Gambia, where strong community and family coherence are important determinants that have to be taken into consideration in promoting lifestyle changes. METHODS We questioned 5389 adults as to any first-degree family history of major noncommunicable diseases (hypertension, obesity, diabetes and stroke), and measured their blood pressure (BP) and body mass index (BMI). Total blood cholesterol, triglyceride, uric acid, and creatinine concentrations were measured in a stratified subsample, as well as blood glucose (2 hours after ingesting 75 g glucose) in persons aged > or = 35 years. FINDINGS A significant number of subjects reported a family history of hypertension (8.0%), obesity (5.4%), diabetes (3.3%) and stroke (1.4%), with 14.6% of participants reporting any of these NCDs. Subjects with a family history of hypertension had a higher diastolic BP and BMI, higher cholesterol and uric acid concentrations, and an increased risk of obesity. Those with a family history of obesity had a higher BMI and were at increased risk of obesity. Individuals with a family history of diabetes had a higher BMI and higher concentrations of glucose, cholesterol, triglycerides and uric acid, and their risk of obesity and diabetes was increased. Subjects with a family history of stroke had a higher BMI, as well as higher cholesterol, triglyceride and uric acid concentrations. CONCLUSIONS A family history of hypertension, obesity, diabetes, or stroke was a significant risk factor for obesity and hyperlipidaemia. With increase of age, more pathological manifestations can develop in this high-risk group. Health professionals should therefore utilize every opportunity to include direct family members in health education.Objetivo Determinar si la existencia de unos antecedentes familiares de alto riesgo de sufrir enfermedades no transmisibles (ENT) constituı́a un factor de riesgo relevante para esas dolencias entre los miembros de la familia en una población de estudio de Gambia, paı́s donde los sólidos lazos comunitarios y la cohesión familiar son determinantes importantes que deben tenerse en cuenta a la hora de promover cambios del estilo de vida. Métodos Pedimos a 5389 adultos que mencionaran cualquier antecedente, entre los familiares de primer grado, de ENT importantes (hipertensión, obesidad, diabetes y accidente cerebrovascular), y medimos su tensión arterial (TA) y su ı́ndice de masa corporal (IMC). Se determinaron las concentraciones de colesterol total, triglicéridos, ácido úrico y creatinina en sangre en una submuestra estratificada, ası́ como la glucosa sanguı́nea (dos horas después de ingerir 75 g de glucosa) en las personas de más de 34 años. Resultados Un número importante de individuos refirieron antecedentes familiares de hipertensión (8,0%), obesidad (5,4%), diabetes (3,3%) y accidente cerebrovascular (1,4%), elevándose al 14,6% los participantes que mencionaron cualquiera de esas ENT. Las personas con antecedentes familiares de hipertensión presentaban una TAdiastólica y un IMC superiores a lamedia, concentracionesmayores de colesterol y de ácido úrico y unmayor riesgo de obesidad. Las personas con historia familiar de obesidad tenı́an un IMC mayor y presentaban un riesgo más elevado de obesidad. Los individuos con antecedentes familiares de diabetes presentaban unmayor IMC, niveles más altos de glucosa, colesterol, triglicéridos y ácido úrico, y unmayor riesgo de obesidad y diabetes. Y los individuos con antecedentes familiares de ictus presentaban un IMC más elevado, ası́ como concentraciones más altas de colesterol, triglicéridos y ácido úrico. Conclusión Unos antecedentes familiares de hipertensión, obesidad, diabetes o accidente cerebrovascular constituyen un factor de riesgo importante de obesidad e hiperlipidemia. Con el aumento de la edad, en este grupo de alto riesgo pueden aparecer más manifestaciones patológicas. Ası́ pues, los profesionales de la salud deben aprovechar cuantas oportunidades tengan de extender a los familiares directos la educación sanitaria.OBJECTIVE: To examine whether a family history of high-risk groups for major noncommunicable diseases (NCDs) was a significant risk factor for these conditions among family members in a study population in the Gambia, where strong community and family coherence are important determinants that have to be taken into consideration in promoting lifestyle changes. METHODS: We questioned 5389 adults as to any first-degree family history of major noncommunicable diseases (hypertension, obesity, diabetes and stroke), and measured their blood pressure (BP) and body mass index (BMI). Total blood cholesterol, triglyceride, uric acid, and creatinine concentrations were measured in a stratified subsample, as well as blood glucose (2 hours after ingesting 75 g glucose) in persons aged 35 years. FINDINGS: A significant number of subjects reported a family history of hypertension (8.0%), obesity (5.4%), diabetes (3.3%) and stroke (1.4%), with 14.6% of participants reporting any of these NCDs. Subjects with a family history of hypertension had a higher diastolic BP and BMI, higher cholesterol and uric acid concentrations, and an increased risk of obesity. Those with a family history of obesity had a higher BMI and were at increased risk of obesity. Individuals with a family history of diabetes had a higher BMI and higher concentrations of glucose, cholesterol, triglycerides and uric acid, and their risk of obesity and diabetes was increased. Subjects with a family history of stroke had a higher BMI, as well as higher cholesterol, triglyceride and uric acid concentrations. CONCLUSION: A family history of hypertension, obesity, diabetes, or stroke was a significant risk factor for obesity and hyperlipidaemia. With increase of age, more pathological manifestations can develop in this high-risk group. Health professionals should therefore utilize every opportunity to include direct family members in health education.

Pilot trial of a pentavalent pneumococcal polysaccharide/protein conjugate vaccine in Gambian infants

BACKGROUND Invasive pneumococcal disease is a major cause of mortality and morbidity in young children in developing countries. Pneumococcal polysaccharide/protein conjugate vaccines, which are likely to be immunogenic in the very young, offer a potential way for preventing these infections. Therefore a pilot safety and immunogenicity study of a five-valent conjugate vaccine has been undertaken in an area of rural Africa where invasive pneumococcal disease is prevalent. METHODS Thirty Gambian infants were vaccinated with 3 doses of a five-valent pneumococcal conjugate vaccine containing 5 micrograms of type 6B, 14, 18, 19F and 23F polysaccharides conjugated to the diphtheria toxin mutant protein CRM197 at the ages of 2, 3 and 4 months; 30 infants received 2 doses at the ages of 2 and 4 months and 30 infants who received three doses of a Haemophilus influenzae type b vaccine acted as controls. Local and systemic reactions were recorded after vaccination and antibody titers were measured by an enzyme-linked immunosorbent assay. RESULTS No serious local or systemic reactions to vaccination were recorded. Antibody responses to each component of the vaccine were demonstrated. One month after immunization with three doses of vaccine, antibody titers were 3 to 11 times higher than before vaccination (postvaccination titers ranged from 2.49 micrograms/ml for type 19 polysaccharide to 7.59 micrograms/ml for type 14). Elevated titers were well-maintained during the subsequent 4 months. Three doses of vaccine induced higher titers than did two doses. Antibody titers increased 2- to 3-fold over the period of immunization in children who received H. influenzae type b vaccine. CONCLUSIONS A five-valent pneumococcal conjugate vaccine proved safe and immunogenic in Gambian infants. However, a vaccine containing a larger number of serotypes will be necessary to achieve a maximal clinical impact.

Safety and immunogenicity of a nonavalent pneumococcal vaccine conjugated to CRM197 administered simultaneously but in a separate syringe with diphtheria, tetanus and pertussis vaccines in Gambian infants.

Background. Unrelenting high morbidity and mortality have mandated that immunogenic vaccines be used to combat pneumococcal disease in infants. Objectives. To evaluate the safety and immunogenicity of a nonavalent pneumococcal conjugate vaccine and the antigenic interaction when administered simultaneously with diphtheria, tetanus and pertussis vaccines. Methods. Two hundred seven infants were randomized to receive three doses of either nonavalent protein conjugate pneumococcal vaccine (PnCV) or inactivated polio vaccine (IPV) at 2, 3 and 4 months of age with routine Expanded Program of Immunization vaccines as scheduled. Vaccinees were visited on Days 1, 2 and 7 to observe local and systemic adverse reactions. Blood was drawn before the first dose and 1 month after the third dose. Antibody concentrations in sera were measured by standardized enzyme-linked immunosorbent assay. Nasopharyngeal carriage of pneumococci was tested at 5 and 9 months of age. Results. No serious reactions were observed. Local induration and tenderness were observed more commonly at the site of administration of diphtheria, tetanus and pertussis vaccines than at the site of administration of IPV or PnCV. Between 79 and 91% achieved ≥1 μg/ml antibody against specific pneumococcal serotypes. Antibody responses to diphtheria and pertussis antigens were similar in both groups; however, antibody response to tetanus toxoid was significantly lower in infants who received PnCV (geometric mean concentration, 11.1 vs. 17.4; P < 0.001). Nasopharyngeal carriage in PnCV-vaccinated children was reduced but not significantly different from those vaccinated with IPV. Conclusion. Simultaneous administration of PnCV with Expanded Program of Immunization vaccines is safe and immunogenic. Immune response to the composite antigens is likely to confer protection.

Genetic regulation of acquired immune responses to antigens of Mycobacterium tuberculosis : a study of twins in West Africa

ABSTRACT The role of genetic factors in clinical tuberculosis is increasingly recognized; how such factors regulate the immune response to Mycobacterium tuberculosis in healthy individuals is unclear. In this study of 255 adult twin pairs residing in The Gambia, West Africa, it is apparent that memory T-cell responses to secreted mycobacterial antigens (85-kDa antigen complex, “short-term culture filtrate,” and peptides from the ESAT-6 protein), as well as to the 65-kDa heat shock protein, are subject to effective genetic regulation. The delayed hypersensitivity response to intradermal tuberculin also demonstrates significant genetic variance, while quantitative T-cell and antibody responses to the 38-kDa cell membrane protein appear to be determined largely by environmental factors. Such findings have implications for vaccine development.

Blood pressure patterns and cardiovascular risk factors in rural and urban Gambian communities

Hypertension is emerging as an important public health problem in sub-Saharan Africa. We studied blood pressure (BP) patterns, hypertension and other cardiovascular risk factors in a rural and an urban area of The Gambia. A total of 5389 adults (⩾15 years) were selected by cluster sampling in the capital Banjul and a rural area around Farafenni. A questionnaire was completed, BP, pulse rate, height and weight were recorded. Glucose was measured 2 h after a 75 g glucose load among participants ⩾35 years (n = 2301); total cholesterol, triglycerides, creatinine and uric acid were measured among a stratified subsample (n = 1075). A total of 7.1% of the study participants had a BP ⩾160/95 mm Hg; 18.4% of them had a BP ⩾140/90 mm Hg. BP was significantly higher in the urban area. BP increased with age in both sexes in both areas. Increasing age was the major independent risk factor for hypertension. Related cardiovascular risk factors (obesity, diabetes and hyperlipidaemia) were significantly more prevalent in the urban area and among hypertensives; 17% of measured hypertensives were aware of this, 73% of people who reported to have been diagnosed as hypertensive before had discontinued treatment; 56% of those who reported being on treatment were normotensive. We conclude that hypertension is no longer rare in either urban or rural Gambians. In the urban site hypertension and related cardiovascular risk factors were more prevalent. Compliance with treatment was low. Interventions aimed at modifying risk factors at the population level, and at improving control of diagnosed hypertension are essential to prevent future increases of cardiovascular morbidity and mortality. In view of limited resources and feasibility of intervention in rural Gambia, these could initially be directed towards urbanised populations.

A glycoprotein pneumococcal conjugate vaccine primes for antibody responses to a pneumococcal polysaccharide vaccine in Gambian children.

BACKGROUND Streptococcus pneumoniae is a major cause of acute respiratory infections and acute bacterial meningitis in children. Pneumococcal polysaccharide vaccines are poorly immunogenic in this highly vulnerable group, but protein polysaccharide conjugate vaccines are likely to be more effective. OBJECTIVES To determine whether immunization of infants with a pneumococcal conjugate vaccine induces immunologic memory. METHODS Eighty-four Gambian children, who had been vaccinated previously with two or three doses of a pentavalent pneumococcal conjugate vaccine (CRM197) or with a Haemophilus influenzae type b (Hib) conjugate vaccine were immunized when approximately 2 years old with a 23-valent pneumococcal polysaccharide vaccine, and a blood sample was obtained 10 days later. Pneumococcal antibody titers in prevaccination and postvaccination sera were measured by enzyme-linked immunosorbent assay and by an opsonophagocytic assay. RESULTS On revaccination with a pneumococcal polysaccharide vaccine, children who had previously received pneumococcal conjugate vaccine had higher antibody concentrations to each of the five polysaccharide components of the conjugate vaccine than did control children. For type 6B polysaccharide, which is poorly immunogenic in young children, postvaccination antibody concentrations were 0.37, 27.6 and 50.9 microg/ml in children who had received no previous pneumococcal immunization or two or three doses of conjugate vaccine, respectively. Type 14 antibodies produced after revaccination were of high avidity and had opsonic activity. CONCLUSION Vaccination of young infants with two or three doses of a pneumococcal conjugate vaccine primes the immune system to respond strongly and rapidly on subsequent exposure to pneumococcal polysaccharide.

Immunization with a pneumococcal capsular polysaccharide vaccine during pregnancy

The feasibility of preventing invasive pneumococcal infections during the first few months of life by immunization during pregnancy has been investigated. One hundred and fifty Gambian women were immunized with either a 23-valent pneumococcal polysaccharide vaccine or a meningococcal polysaccharide vaccine during the last trimester of pregnancy. Pregnant women showed a good antibody response to five of the six pneumococcal polysaccharides tested (types 1, 3, 5, 6, 14 and 19) but not to type 6 polysaccharide. Mean cord blood/maternal blood IgG antibody ratios varied from 24% (type 1) to 49% (type 3) and differed substantially between individual mother/infant pairs. Pneumococcal antibody levels were higher at birth in infants of women immunized with pneumococcal polysaccharide vaccine than in control infants. However, these antibodies disappeared rapidly during the first few months of life and it is uncertain how much clinical protection against pneumococcal infection maternal immunization would have provided.

Nationwide prevalence study of hypertension and related non‐communicable diseases in The Gambia

The prevalence of hypertension, diabetes and obesity in The Gambia was assessed in a 1% population sample of 6048 adults over 15 years of age. 572 (9.5%) subjects were hypertensive according to WHO criteria (a diastolic blood pressure (DBP) of 95 mmHg or above and/or a systolic blood pressure (SBP) of 160 mmHg or above); 325 (5.4%) had a DBP of 95 mmHg or above, and 39 (2.3%) a DBP of 105 mmHg or above; 428 (7.1%) had a SBP of 160 mmHg or above. By less conservative criteria (a DBP of 90 mmHg or above and/or SBP of 140 mmHg or above), 24.2% of subjects were hypertensive. The prevalence of hypertension was similar in the major ethnic groups and in urban and rural communities. Age and obesity were risk factors for hypertension; female sex was an additional risk factor for diastolic hypertension. Several communities had a prevalence of diastolic hypertension double the national rate, and significant community clustering of diastolic hypertension (P < 0.01) was confirmed by Monte Carlo methods. Genetic and/or localized environmental factors (such as diet or Schistosoma haematobium infection), may be involved. 140 (2.3%) subjects were obese. Obesity was associated with female sex, increasing age, urban environment, non‐manual work and diastolic hypertension. Only 14 (0.3%) subjects were found to be diabetic. Hypertension appears to be very prevalent in The Gambia, with a substantial population at risk of developing target organ damage. Further studies to delineate this risk and appropriate interventions to reduce it are needed.